Search Results (126)

Minimizing carbon dioxide emissions is crucial due to the generation of energy from fossil fuels. The significance of carbon capture and storage (CCS) technology, which is highly successful in mitigating carbon emissions, has increased. On the other hand, hydrogen is an important energy carrier for storing and transporting energy, and technologies that rely on hydrogen have become increasingly promising as the world moves toward a more environmentally friendly approach. Nevertheless, the integration of CCS technologies into power production processes is a significant challenge, requiring the enhancement of the combined power generation–CCS process. In recent years, there has been a growing interest in process intensification (PI), which aims to create smaller, cleaner, and more energy efficient processes. The goal of this research is to demonstrate the process intensification potential and to model and simulate a hybrid integrated–intensified adsorptive-membrane reactor process for simultaneous carbon capture and hydrogen production. A comprehensive, multi-scale, multi-phase, dynamic, computational fluid dynamics (CFD)-based process model is constructed, which quantifies the various underlying complex physicochemical phenomena occurring at the pellet and reactor levels. Model simulations are then performed to investigate the impact of dimensionless variables on overall system performance and gain a better understanding of this cyclic reaction/separation process. The results indicate that the hybrid system shows a steady-state cyclic behavior to ensure flexible operating time. A sustainability evaluation was conducted to illustrate the sustainability improvement in the proposed process compared to the traditional design. The results indicate that the integrated–intensified adsorptive-membrane reactor technology enhances sustainability by 35% to 138% for the chosen 21 indicators. The average enhancement in sustainability is almost 57%, signifying that the sustainability evaluation reveals significant benefits of the integrated–intensified adsorptive-membrane reactor process compared to HTSR + LTSR. Full article

Excessive carbon dioxide (CO₂) emissions represent a critical challenge in mitigating global warming, necessitating advanced separation technologies for efficient carbon capture. Silica-based membranes have attracted significant attention due to their exceptional chemical, thermal, and mechanical stability under harsh operating conditions. In this study, we introduce a novel layered hybrid membrane designed based on amine-functionalized silica precursors, where a distinct affinity gradient is engineered by incorporating two types of amine-functionalized materials. The top layer was composed of high-affinity amine species to maximize CO₂ sorption, while a sublayer with milder affinity facilitated smooth CO₂ diffusion, thereby establishing a continuous solubility gradient across the membrane. A dual approach, combining comprehensive experimental testing and rigorous theoretical modeling, was employed to elucidate the underlying CO₂ transport mechanisms. Our results reveal that the hierarchical structure significantly enhances the intrinsic driving force for CO₂ permeation, leading to superior separation performance compared to conventional homogeneous facilitated transport membranes. This study not only provides critical insights into the design principles of affinity gradient membranes but also demonstrates their potential for scalable, high-performance CO₂ separation in industrial applications. Full article

Membrane-based direct air capture of CO₂ (m-DAC) is a promising solution for atmospheric decarbonization. Despite growing interest, the impact of relative air humidity on the performance of m-DAC systems is often neglected in the literature. This study presents detailed parametric analyses that take into account humidity variability and several hypothetical scenarios regarding membrane selectivity toward water vapor. Specifically, cases were considered where the permeance of H₂O relative to CO₂ was assumed to be 0.5, 2, and 5 times higher, which allowed for a systematic assessment of the impact of relative humidity on process performance. The calculations were carried out both for membranes with assumed separation parameters and for the PolyActive^TM membrane, enabling a realistic evaluation of the influence of atmospheric conditions on the process. The results show that an increase in humidity in the analyzed range from 0 to 80% can lead to a rise in the energy intensity of the process by up to approximately 34%, and an increase in total power demand by around 29%. As humidity increases, key process parameters such as CO₂ purity in the permeate and recovery rate decrease. The water vapor content in the permeate in a single-stage membrane separation process can reach up to 60%. It is recommended to use gas drying systems and to develop membranes with low H₂O permeance in order to reduce the energy cost of the process. The potential location of m-DAC systems should preferably be in regions with low air humidity. The study highlights the necessity of considering local climate conditions and the need for further research on membrane selectivity. Full article

This present study covers a complex approach to study a hybrid separation technique: membrane-assisted gas absorption for CO₂ capture from flue gases. It includes not only the engineering aspects of the process, particularly the cell design, flow organization, and process conditions, but also a complex study of the materials. It covers the spinning of hollow fibers with specific properties that provide sufficient mass transfer for their implementation in the hybrid membrane-assisted gas absorption technique and the design of an absorbent with a new ionic liquid—bis(2-hydroxyethyl) dimethylammonium glycinate, which allows the selective capture of carbon dioxide. In addition, the obtained hollow fibers are characterized not only by single gas permeation but with regard to mixed gases, including the transfer of water vapors. A quasi-real flue gas, which consists of nitrogen, oxygen, carbon dioxide, and water vapors, is used to evaluate the separation efficiency of the proposed membrane-assisted gas absorption technique and to determine its ultimate performance in terms of the CO₂ content in the product flow and recovery rate. As a result of this study, it is found that highly permeable fibers in combination with the obtained absorbent provide sufficient separation and their implementation is preferable compared to a selective but much less permeable membrane. Full article

Global warming, driven significantly by carbon dioxide (CO₂) emissions, necessitates immediate climate action. Consequently, CO₂ capture is essential for mitigating carbon output from industrial and power generation processes. This study investigates the effect of absorbent temperature on CO₂ separation performance using gas–liquid polymeric hollow fiber membrane (HFM) contactors. It summarizes the relationship between liquid-phase temperature and CO₂ capture efficiency across various physical and chemical absorption processes. Twelve relevant studies (nine experimental, three mathematical), providing a comprehensive database of 104 individual measurements, were rigorously analyzed. Liquid-phase temperature significantly influences CO₂ separation performance in HFM contactors. In particular, the present analysis reveals that, overall, for every 10 °C temperature increase, physical absorption performance decreases by approximately 3%, while chemical absorption performance improves by 3%, regardless of other parameters. This empirical law was confirmed by direct comparisons with additional experimental results. Strategies for further development of these processes are also proposed. Full article

Carbon dioxide (CO₂) capture is a pivotal technology for achieving the goal of carbon neutrality. This paper proposes a novel process, SBS + SI, which integrates Solution Blow Spinning (SBS) and Solution Impregnation Method (SI), using polyamide 66 (PA66) as the carrier material and high-purity tetraethylenepentamine (TEPA) as the modifier, to fabricate nanofiber adsorption membranes with varying carrier structures and modifier component loadings. The CO₂ adsorption performance and pore structure of the adsorbents were investigated using characterization techniques, such as Scanning Electron Microscopy (SEM), Thermogravimetric Analysis (TGA), Brunauer-Emmett-Teller (BET) surface area and pore size analysis, and Fourier Transform Infrared Spectroscopy (FT-IR). The results indicate that as the mass fraction of TEPA increases, the pores in the nanofiber membranes gradually decrease, while the CO₂ adsorption capacity significantly increases. The PA66 nanofiber membrane achieves peak CO₂ capture performance (44.7 mg/g at 25 °C) at 15% TEPA loading. Meanwhile, the composite nanofiber membranes also exhibit outstanding CO₂/N₂ selectivity with a separation factor reaching 28. Thermal regeneration tests at 90 °C confirm the composite’s outstanding cyclic stability and regenerability, demonstrating its potential for practical carbon capture applications. These findings suggest that the nanofiber adsorbents prepared by the SBS + SI process have broad application prospects in the field of CO₂ capture. Full article

In an integrated gasification combined cycle (IGCC), a gasification process produces a gas stream from a solid fuel, such as coal or biomass. This gas (syngas or synthesis gas) resulting from the gasification process contains carbon monoxide, molecular hydrogen, and carbon dioxide (other gaseous components may also be present depending on the gasified solid fuel and the gasifying agent). Separating hydrogen from this syngas stream has advantages. One of the methods to separate hydrogen from syngas is selective permeation through a palladium-based metal membrane. This separation process is complicated as it depends nonlinearly on various variables. Thus, it is desirable to develop a simplified reduced-order model (ROM) that can rapidly estimate the separation performance under various operational conditions, as a preliminary stage of computer-aided engineering (CAE) in chemical processes and sustainable industrial operations. To fill this gap, we present here a proposed reduced-order model (ROM) procedure for a one-dimensional steady plug-flow reactor (PFR) and use it to investigate the performance of a membrane reactor (MR), for hydrogen separation from syngas that may be produced in an integrated gasification combined cycle (IGCC). In the proposed model, syngas (a feed stream) enters the membrane reactor from one side into a retentate zone, while nitrogen (a sweep stream) enters the membrane reactor from the opposite side into a neighbor permeate zone. The two zones are separated by permeable palladium membrane surfaces that are selectively permeable to hydrogen. After analyzing the hydrogen permeation profile in a base case (300 °C uniform temperature, 40 atm absolute retentate pressure, and 20 atm absolute permeate pressure), the temperature of the module, the retentate-side pressure, and the permeate-side pressure are varied individually and their influence on the permeation performance is investigated. In all the simulation cases, fixed targets of 95% hydrogen recovery and 40% mole-fraction of hydrogen at the permeate exit are demanded. The module length is allowed to change in order to satisfy these targets. Other dependent permeation-performance variables that are investigated include the logarithmic mean pressure-square-root difference, the hydrogen apparent permeance, and the efficiency factor of the hydrogen permeation. The contributions of our study are linked to the fields of membrane applications, hydrogen production, gasification, analytical modeling, and numerical analysis. In addition to the proposed reduced-order model for hydrogen separation, we present various linear and nonlinear regression models derived from the obtained results. This work gives general insights into hydrogen permeation via palladium membranes in a hydrogen membrane reactor (MR). For example, the temperature is the most effective factor to improve the permeation performance. Increasing the absolute retentate pressure from the base value of 40 atm to 120 atm results in a proportional gain in the permeated hydrogen mass flux, with about 0.05 kg/m².h gained per 1 atm increase in the retentate pressure, while decreasing the absolute permeate pressure from the base value of 20 bar to 0.2 bar causes the hydrogen mass flux to increase exponentially from 1.15 kg/m².h. to 5.11 kg/m².h. This study is linked with the United Nations Sustainable Development Goal (SDG) numbers 7, 9, 11, and 13. Full article

The efficient separation and removal of carbon dioxide (${CO}_2$) from its mixtures is an important technological challenge to limit effects resulting from the increase of the carbon dioxide concentration in the atmosphere. Membrane technology is an environmentally friendly approach, highly scalable and less energy-consuming than conventional methods such as adsorption, absorption and cryogenic separation. Hybrid membrane materials incorporating inorganic filler nanostructures in polymer matrices having polyethylene glycol (PEG) as a plasticized additive are promising membrane materials given the presence of ${CO}_2$-philic polar functional groups of PEGs and the structural refinements on the blend matrix consequent to the filler distribution. In this review, literature information on hybrid polymer/PEG membranes are critically reviewed to discuss how filler dispersion in the blend matrix gives rise to enhanced ${CO}_2$ separation performances with respect to those obtained with traditional mixed matrix membranes where filler nanostructures are dispersed in the neat polymer. The discussion will be focused on the correlation between the ${CO}_2$ transport properties, membrane structural properties and defect resulting from the polymer-filler incompatibility. It is shown that hybrid polymer/PEG membranes with dispersed filler nanostructures simultaneously offer improved ${CO}_2$ separation performances and enhanced mechanical properties compared with nanocomposite ones where filler particles are dispersed in the neat polymer matrix. PEG addition enhances the filler-matrix compatibility, delays filler aggregation and limits the formation of filler-matrix interface defects. Full article

Excessive (carbon dioxide) CO₂ emissions are a primary factor contributing to climate change. As one of the crucial technologies for alleviating CO₂ emissions, carbon capture and utilization (CCU) technology has attracted considerable global attention. Technologies for capturing CO₂ in extreme circumstances are indispensable for regulating CO₂ levels in industrial processes. The unique separation characteristics of the ceramic–carbonate dual-phase (CCDP) membranes are increasingly employed for CO₂ separation at high temperatures due to their outstanding chemical, thermal durability, and mechanical strength. This paper presents an overview of CO₂ capture approaches and materials. It also elaborates on the research progress of three types of CCDP membranes with distinct permeation mechanisms, concentrating on their principles, materials, and structures. Additionally, several typical membrane reactors, such as the dry reforming of methane (DRM) and reverse water–gas shift (RWGS), are discussed to demonstrate how captured CO₂ can function as a soft oxidant, converting feedstocks into valuable products through oxidation pathways designed within a single reactor. Finally, the future challenges and prospects of high-temperature CCDP membrane technologies and their related reactors are proposed. Full article

With the consequences of climate change becoming more urgent, there has never been a more pressing need for technologies that can help to reduce the carbon dioxide (CO₂) emissions of the most polluting sectors, such as power generation, steel, cement, and the chemical industry. This review summarizes the state-of-the-art technologies for carbon capture, for instance, post-combustion, pre-combustion, oxy-fuel combustion, chemical looping, and direct air capture. Moreover, already established carbon capture technologies, such as absorption, adsorption, and membrane-based separation, and emerging technologies like calcium looping or cryogenic separation are presented. Beyond carbon capture technologies, this review also discusses how captured CO₂ can be securely stored (CCS) physically in deep saline aquifers or depleted gas and oil reservoirs, stored chemically via mineralization, or used in enhanced oil recovery. The concept of utilizing the captured CO₂ (CCU) for producing value-added products, including formic acid, methanol, urea, or methane, towards a circular carbon economy will also be shortly discussed. Real-life applications, e.g., already pilot-scale continuous methane (CH₄) production from flue gas CO₂, are shown. Actual deployment of the most crucial technologies for the future will be explored in real-life applications. This review aims to provide a compact view of the most crucial technologies that should be considered when choosing to capture, store, or convert CO₂, informing future researchers with efforts aimed at mitigating CO₂ emissions and tackling the climate crisis. Full article

Membrane technology is a promising methodology for carbon dioxide separation due to its benefit of a small carbon footprint. However, the trade-off relationship between gas permeability and selectivity is one obstacle to limiting its application. Herein, branched polyethyleneimine (BPEI) containing a rich amino group was successfully grafted on the surface of the metal–organic framework (MOF) of AIFFIVE-1-Ni (KAUST-8) through coordination between N in BPEI and open metal sites in the MOF and with the resultant maintained BET surface area and pore volume. Both the strengthened CO₂ solubility coefficients coming from the additional CO₂ adsorption sites of amino groups in BPEI and the reinforced CO₂ diffusivity coefficients originating from the fast transport channels created by KAUST-8 led to the promising CO₂ separation performance for KAUST-8@BPEI/Pebax-1074 MMM. With 5 wt.% KAUST-8@BPEI loading, the MMM showed the CO₂ permeability of 156.5 Barrer and CO₂/N₂ selectivity of 16.1, while the KAUST-8-incorporated MMM (5 wt.% loading) only exhibited the CO₂ permeability of 86.9 Barrer and CO₂/N₂ selectivity of 13.0. Such enhancement is superior to most of the reported Pebax-1074-based MMMs for CO₂ separation indicating a wide application for the coordination method for MOF fillers with open metal sites. Full article

A critical issue facing extraterrestrial expansion has always been long-term life support capabilities. The large energy requirements to move even small amounts of material from Earth necessitate the ability to reuse and recycle as much as possible, particularly waste. The weight of food supplies eventually starts to limit the length of the expedition. Hydroponic growth systems offer the ability to grow plants, and with them, a miniature ecosystem. This offers the ability to repurpose both carbon dioxide and waste salts such as ammonia and other compounds, such as those found in urine. A major issue facing hydroponic systems is the need to provide a stable water-based nutrient stream. Direct contact membrane distillation (DCMD) was tested for viability as a method of re-concentrating and stabilizing the nutrient-rich water stream. Polytetrafluoroethylene (PTFE)- and polyvinylidene (PVDF)-based polymer hydrophobic membranes were used to separate solutes from water. The DCMD method was tested with the feed stream operating at temperatures of 50 °C, 65 °C, and 80 °C. The results were analyzed using UV-Visible spectroscopy to determine concentrations. The benefits and limitations of the PTFE and PVDF membranes in DCMD were compared. The larger-pore PTFE membranes concentrated solutions effectively at 80 °C, while the PVDF membranes removed more water at lower temperatures, but permitted detectable phosphate ion leakage. Adjusting temperature and flow rates can help maintain stable ion and water transfer, benefiting hydroponic systems in achieving reliable nutrient levels. Full article

The production of hydrogen via dark fermentation generates carbon dioxide, which needs to be separated and re-utilized to minimize the environmental impact. This research investigates the potential of utilizing algae for carbon dioxide sequestration in hydrogen production via dark fermentation. However, algae alone cannot fully use all the carbon dioxide produced, necessitating the implementation of a multistage separation process. This study proposes a purification approach that integrates membrane separation with a photobioreactor in a multistage design layout. Mathematical models were used to simulate the performance efficiency of multistage design layout using MATLAB 2015b (Version 9.3). A detailed parametric analysis and the key parameters influencing the separation efficiency were conducted for each stage. This study explores how reactor geometry, operational dynamics (such as gas transfer rates and light availability), and algae growth impact both CO₂ removal and hydrogen purity. An optimization strategy was used to obtain the set of optimal operating and design parameters. Our results have shown a significant improvement in hydrogen purity, increasing from 55% to 99% using this multistage separation process, while CO₂ removal efficiency rose from 35% to 85% over a week. This study highlights the potential of combining membrane technology with photobioreactors to enhance hydrogen purification, offering a more sustainable and efficient solution for hydrogen production. Full article

Due to carbon dioxide (CO₂) levels, driven by our reliance on fossil fuels and deforestation, the challenge of global warming looms ever larger. The need to keep the global temperature rise below 1.5 °C has never been more pressing, pushing us toward innovative solutions. Enter carbon capture, utilization, and storage (CCUS) technologies, our frontline defense in the fight against climate change. Imagine a world where CO₂, once a harbinger of environmental doom, is transformed into a tool for healing. This review takes you on a journey through the realm of CCUS, revealing how these technologies capture CO₂ from the very sources of our industrial and power activities, repurpose it, and lock it away in geological vaults. We explore the various methods of capture—post-combustion, oxy-fuel combustion, and membrane separation—each with their own strengths and challenges. But it is not just about science; economics play a crucial role. The costs of capturing, transporting, and storing CO₂ are substantial, but they come with the promise of a burgeoning market for CO₂-derived products. We delve into these financial aspects and look at how captured CO₂ can be repurposed for enhanced oil recovery, chemical manufacturing, and mineralization, turning waste into worth. We also examine the landscape of commercial-scale CCS projects, highlighting both global strides and regional nuances in their implementation. As we navigate through these advancements, we spotlight the potential of Artificial Intelligence (AI) to revolutionize CCUS processes, making them more efficient and cost-effective. In this sweeping review, we underscore the pivotal role of CCUS technologies in our global strategy to decarbonize and forge a path toward a sustainable future. Join us as we uncover how innovation, supportive policies, and public acceptance are paving the way for a cleaner, greener world. Full article

Lithium–sulfur batteries (LSBs) exhibit high theoretical specific capacities, abundant resource reserves, and low costs, making them promising candidates for next-generation lithium-ion batteries (LIBs). However, significant challenges, such as the shuttle effect and volume expansion, hinder their practical applications. To address these issues, this study introduces a unique intermediate layer comprising N-doped carbon nanofiber/TiO₂/diatomite (NCNF/TiO₂/DE) from the perspective of membrane modification. The intermediate layer comprises nitrogen-doped titanium dioxide/carbon nanofiber (NCNF/TiO₂) materials, with diatomite filling the fiber gaps. This forms a three-dimensional (3D) conductive network that provides ample space for sulfur volume expansion and numerous adsorption active sites, thereby accelerating electrolyte penetration and lithium-ion diffusion. These features collectively contribute to the outstanding electrochemical performance of the battery. At 0.1 C, the NCNF/TiO₂/DE-800-coated separator battery achieved a first-cycle discharge specific capacity of 1311.1 mAh g⁻¹, significantly higher than the uncoated lithium–sulfur battery (919.6 mAh g⁻¹). Under varying current densities, the NCNF/TiO₂/DE-800 material demonstrates good electrochemical reversibility and exhibits high lithium-ion diffusion rates and low charge-transfer resistance. Therefore, this study provides an advanced intermediate layer material that enhances the electrochemical performance of lithium–sulfur batteries. Full article